Return to Noise Assessment  Noise Assessment    Project Summary ::    1   2   3   4   5   6   7      Background The Vermont Agency of Transportation (VTrans) is planning to expand the Circumferential Highway (VT 289). Resource Systems Group was retained by VTrans to assess potential roadway noise-related impacts arising from the proposed expansion, for a number of locations near the alignment of a proposed section. A roadway noise study was required for the project's revised Environmental Assessment (EA). Project Scope •  Installed sound level monitoring equipment to measure existing ambient sound levels. •  Scheduled sound level monitoring in conjunction with a VTrans traffic count for an existing segment VT 289. In this, automated continuous traffic counters measured total traffic volume and vehicle type, while sound level monitors measured sound levels. •  Developed a computer-based traffic noise prediction model of VT 289 and nearby roadways, including Interstate 89 (I-89), using the Federal Highway Administration's (FHWA) Traffic Noise Model (TNM). •  Incorporated a number of different data sources into the TNM model to represent topography, vegetation, roadway geometry, roadway speed limits and roadway traffic volumes. •  Validated TNM model results with measured traffic and sound level data. •  Reviewed TNM results according to state and federal guidelines to determine if noise impacts would occur from the proposed project. Project Results Monitoring results combined with field observations indicated that ambient sound levels in the project area are largely due to roadway noise from I-89. Model-predicted results indicated that Noise Abatement Criteria (NAC) will not be exceeded and that no substantial increase in noise levels would occur in any scenario. This is due, in part, to sound attenuation by two existing berms, which were built in anticipation of the project. Study results were incorporated in the updated Environmental Assessment for the proposed project.